delBarco-Trillo J, Roldan E R S
Reproductive Ecology and Biology Group, Museo Nacional de Ciencias Naturales, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain.
J Evol Biol. 2014 Jan;27(1):55-62. doi: 10.1111/jeb.12275. Epub 2013 Nov 20.
The sperm membrane is a key structure affecting sperm function and thus reproductive success. Spermatozoa are highly specialized and differentiated cells that undergo a long series of processes in the male and female reproductive tracts until they reach the site of fertilization. During this transit, the sperm membrane is prone to damage such as lipid peroxidation. The characteristics and performance of the sperm membrane are strongly determined by the fatty-acid composition of membrane phospholipids. Polyunsaturated fatty-acids (PUFAs) are the most prone to lipid peroxidation. Lipid peroxidation and other types of oxidative damage increase with higher metabolism and with higher levels of sperm competition due to the increased ATP production to fuel higher sperm velocities. Consequently, we hypothesized that, in order to avoid oxidative damage, and the ensuing impairment of sperm function, sperm cells exhibit a negative relationship between PUFA content and mass-specific metabolic rate (MSMR). We also hypothesized that higher sperm competition leads to a reduction in the proportion of sperm PUFAs. We performed a comparative study in mammals and found that high MSMR and high levels of sperm competition both promote a decrease in the proportion of PUFAs that are more prone to lipid peroxidation. The negative relationship between MSMR and these PUFAs in sperm cells is surprising, because a positive relationship is found in all other cell types so far investigated. Our results support the idea that the effects of MSMR and sperm competition on sperm function can operate at very different levels.
精子膜是影响精子功能进而影响生殖成功的关键结构。精子是高度特化和分化的细胞，在雄性和雌性生殖道中经历一系列漫长的过程，直至到达受精部位。在这个过程中，精子膜容易受到诸如脂质过氧化等损伤。精子膜的特性和性能在很大程度上由膜磷脂的脂肪酸组成决定。多不饱和脂肪酸（PUFAs）最容易发生脂质过氧化。由于产生更多的ATP以支持更高的精子速度，脂质过氧化和其他类型的氧化损伤会随着新陈代谢加快和精子竞争水平提高而增加。因此，我们推测，为了避免氧化损伤以及随之而来的精子功能受损，精子细胞中PUFA含量与质量特异性代谢率（MSMR）之间呈负相关。我们还推测，更高的精子竞争会导致精子中PUFA比例降低。我们在哺乳动物中进行了一项比较研究，发现高MSMR和高水平的精子竞争都会促使更容易发生脂质过氧化的PUFA比例下降。精子细胞中MSMR与这些PUFA之间的负相关关系令人惊讶，因为在迄今为止研究的所有其他细胞类型中都发现是正相关关系。我们的结果支持这样一种观点，即MSMR和精子竞争对精子功能的影响可以在非常不同的层面上起作用。
